Robust constraints on dark energy and gravity from galaxy clustering data

Abstract

Galaxy clustering data provide a powerful probe of dark energy. We examine how the constraints on the scaled expansion history of the Universe, xh(z) =H(z)s (with s denoting the sound horizon at the drag epoch), and the scaled angular diameter distance, xd(z) =DA(z)/s, depend on the methods used to analyse the galaxy clustering data. We find that using the observed galaxy power spectrum, Pobsg(k), xh(z) and xd(z) are measured more accurately and are significantly less correlated with each other, compared to using only the information from the baryon acoustic oscillations (BAO) in Pobsg(k). Using the {xh(z), xd(z)} from Pobsg(k) gives a Dark Energy Task Force (DETF) dark energy figure of merit (FoM) approximately a factor of 2 larger than using the {xh(z), xd(z)} from BAO only; this provides a robust conservative method to go beyond BAO only in extracting dark energy information from galaxy clustering data. We find that a Stage IV galaxy redshift survey, with 0.7 < z < 2 over 15 000 (deg)2, can measure with high precision [where fg(z) and G(z) are the linear growth rate and factor of large‐scale structure, respectively, and is the dimensionless normalization of Pobsg(k)], when redshift‐space distortion information is included. The measurement of provides a powerful test of gravity, and significantly boosts the dark energy FoM when general relativity is assumed.

Towards more realistic forecasting of dark energy constraints from galaxy redshift surveys

“…Next, we will present results for StageIV+BOSS spectroscopic galaxy redshift surveys, and compare these with those from the previously widely adopted approach derived from and developed in detail in Wang (2012). No priors are used in deriving {x h (z), x d (z), fg(z)σm(z)/s α } constraints for future surveys, since these provide modelindependent constraints on the cosmic expansion history and the growth rate of cosmic large scale structure.…”

“…To avoid the direct measurement of the unknown galaxy bias b(z), we rewrite our model for the measured galaxy power spectrum as (Wang 2012)…”

“…This full Fisher matrix, or a smaller set marginalized over various parameters, is projected into the standard set of cosmological parameters {w0, wa, ΩX , Ω k , ωm, ω b , ns, ln As}. There are four different ways of utilizing the information from P (k) (Wang 2012).…”

Improving Fisher matrix forecasts for galaxy surveys: window function, bin cross-correlation and bin redshift uncertainty

“…The number density of galaxies n(z) is estimated using the latest empirical data (see Table 3 in (Amendola et al 2013) and Figure 3.2 in (Laureijs et al 2011)). We follow the commonly employed procedure in galaxy clustering Fisher matrix forecasts, such that within each bin the galaxy density n(z i ) is assumed to be constant (see (Seo & Eisenstein 2003;Amendola et al 2005;Wang 2006;Albrecht et al 2009;Di Porto et al 2012;Wang 2012;Xu et al 2014)).…”

Neutrinos and dark energy constraints from future galaxy surveys and CMB lensing information

“…The k max is chosen in a way to exclude information from non linear regime where equation 34 is inaccurate (see [40]). For an approach considering the non-linear regime see, for example, [41][42][43][44]. Moreover, for the impact of precisely modeling systematic effects, such as the non-linear clustering and redshift space distortions, in the evolution of BAO see [45][46][47].…”